Present day tendencies in the field of locks is to provide locking devices in which a mechanical key, conventionally used together with a mechanical lock, is avoided due to the reduced number of different keys which can be made for each type and the ease in opening by means of picklocks. An increase in the number of points of such locks has been suggested to thereby increase the number of combinations, but a mechanical problems and the substantial increase in price have resulted.
There are known devices which, by means of electric, contacts having calibrated resistances, light conductions, etc., produce electric pulses which, when combined, electrically activate a bolt.
Another device activates magnetised pieces, located in the interior of the receiver of the key body, by means of other magnetised pieces, located in the interior of the key body, so that when arranged in a programmed position they permit a mechanical movement or they control electrical contacts for the activation of moment of a bolt.
In other devices the key body is comprised of cards having electric or magnertic circuits which, when inserted in a receiver, are read by reading heads and transmit, by means of a computer, an opening signal to the bolt.
These devices have various and different disadvantages. All these systems in general, and those based on printed cards in particular, are extremely expensive and highly complex, wherefore they are not accessible to the general public. Activation of any of these systems which use any type of contact between the key body and the receiver of the key body may be prevented by dirt, such as dust, grease, etc. or any other obstacle.
In general, all systems which use an accessible receiver in which the opening code or key is contained, can be activated by persons skilled in the art. This occurs with locks having a mechanical key and with those having magnets operating on other magents. Besides the latter locks can be operated without the appropriate key since the magnets situated in the receiver provide an indication of the position of the magnets contained in the key body, wherefore a negative of the key is readily obtainable.
Furthermore, in any system which individually differentiates the receiver of the key body for each unit and whose operating code is, therefore, in the receiver, can be operated by an expert, and since the receiver is not an identical piece, it cannot be mass-produced at a low cost.